The invention relates to conveyor assemblies with grippers for discrete products or groups of discrete products. More particularly, the invention relates to improvements in gripper conveyor assemblies which can be utilized with advantage for the transport of sheet-like products (such as sections of newspapers) between a pickup station and a delivery station.
Presently known gripper conveyor assemblies for sheet-like products normally employ chains which serve to transport a set of spaced-apart grippers along a preselected path. The links of the chain in a conventional conveyor are connected to each other by universal joints. Reference may be had, for example, to German Pat. No. 1,206,228, to published German patent application No. 26 29 528, to U.S. Pat. No. 4,638,906 and to U.S. Pat. No. 4,746,007. Each gripper has rollers designed to move along tracks which are defined by a metallic guide. Each chain is an endless chain which is driven by at least one sprocket wheel.
Grippers which are used in the above outlined chain conveyor assemblies have pairs of jaws which can engage discrete products during transport between the pickup and delivery stations. Certain other types of grippers are described and shown in Swiss Pat. No. 592 562 and in European Pat. No. 0 095 602. The grippers can engage successive products of a stream of products which are disposed end-to-end, or successive products which form a scalloped stream of partly overlapping products.
A drawback of heretofore known gripper conveyor assemblies is that the metallic guide for the roller followers of links of the chain conveyor must be machined and/or otherwise finished with a very high degree of precision which contributes significantly to the manufacturing cost. A high degree of precision in the making and/or mounting of a metallic guide is necessary because even minor deviations from optimum dimensions can cause the generation of pronounced noise which is attributable to rolling movement of the followers of the links along their track or tracks. Another drawback of conventional chain conveyor assemblies is that the cost of a chain which consists of numerous discrete links with universal joints between them is very high. Moreover, each link is provided with at least one roller follower which also contributes to the cost of the chain. The bulk and weight of a chain are considerable, especially in comparison with the weight of conveyed products. The weight of the chain conveyor plays a considerable role when the conveyor assembly is installed in a newspaper printing plant or in another establishment for the making, assembling and other processing of printed products wherein the products must be transported between several storeys and along elongated paths which can cover a distance of several hundred yards or even longer. The links of the chains, the joints and the followers are subjected to extensive wear so that they generate high maintenance, repair and replacement costs.
Another drawback of conventional gripper conveyor assemblies is that the grippers are heavy, bulky and expensive.